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NITED' v STATES PATENT @rrron.

ARTHUR SMITH, OF BROGKLEY, COUNTY OF KENT,- ENGLAND.

MANUFACTURE OF CARBONS FOR ELECTRIC LIGHTS.

SPECIFICATION forming part of Letters Patent No. 301,929, dated July 15, 1884.

\ Application filed February 6, 1884. (No specimens.) Patented in England March 27, 1882, No. 1,465; in France September 22, 1882,

No. 151,232; in Belgium September 27, 1882, No. 59,129, and in Germany September 27, 1882, No. 23,732.

. No. 1,465; France, dated September 22, 1882,

No. 151,232; Belgium, dated September 27, 1882, No. 59,129; Germany, dated September 27, 1882, No. 23,732,) and I do hereby declare that the following is a full, clear, and exact description of the invention, which will enable others skilled in the art to which it appertai-ns to make and use the same.

My invention relates to the production of carbons for electric lamps in the form of filaments of high resistance for incandescent lamps, or of rods for are lamps.

For producing filaments I pass through the liquid furfurol or fucusol hydrochloric-acid gas in excess, taking care to keep the liquid The reaction produces a'black liquid, which I inclose between two glass plates kept apart at a distance equivalent to the desired thickness of filament, for which purpose pieces of wire or thread of equivalent diameter may be interposed between the plates. After the material has thoroughly set, which requires fromeight to twelve hours, I carefully wedge the plates apart, and place that to which the film adheres in cold water for about half an hour, in which time the sheet of carbon will detach itself. This sheet is then floated onto a fiat surface of woodor cardboard, which may be cemented on a sheet of plate-glass by shellac varnish. The excess of moisture is removed by blotting-paper, and the adhering sheet is cut into strips of any required width by a sharp knife. I bend these strips between molds, of horseshoe or other suitable form, made of plaster-of-paris, and'expose them to a temperature of two hundred and twelve degrees (212) Fahrenheit. A number of the strips may be bent together round a glass tube, with their ends secured by two threads passed outside and inside the tube longitudinally. The strips thus bent form elastic rings of carbon. The filaments, when removed from the molds or the glass tube, are subjected to a high heat in closely-covered crucibles surrounded with carbon powder, or inporcelain tubes partly filled with carbon powder, through which a current of coal-gas is passed during the process. According to another method, I pour on the glass plate a mixture of about three parts of furfurol or fucusol, with one part of commercial vitriol ofspecific gravity about 1.84, (one, decimal, eighty-four,) and when the material is set I treat it as before described. The electrical resistance of the filaments may be varied by mixing about two and a half (25-) per cent. of lamp-black with the furfurol or fucusol before treatment.

For producing carbon rods for SJCIEUHPS, I mix lamp-black or any finely-divided carbon with about sixty or seventy per cent. of furfurol or fucusol and subject the mixture to compression in slightly-tapered molds, or force the pasty mass through a die; or, according to another method, dry lamp-black may be strongly compressed into molds, so as to form rods, which, on being dipped for a moment in a bath of furfurol or fucusol, become thoroughlyimpregnated therewith. The molded or impregnated rods are then subjected to an atmosphere of hydrochloric-acid gas in vessels or tanks. which may be madeof wood or slate saturated. with paraffine. After remaining from twelve to twenty-four hours exposed to the gas, they are removed, and, if necessary,

they may be saturated by being dipped a second time into thefurfurol or fucusol, and again exposed to the acid gas. Such cracks as may appear in the rods may be fillcd witha paste of carbon and furfurol or fucusol.

The rods are finished, as usual, by,highly heat- 7 ing them in close vessels, in which they are covered with charcoal-powder. Although I have mentioned hydrochloricacid gas as the reagent employed, other hydrogen acidssuch as hydrofluoric, hydriodic, or hydrobromic acid-may be employed; but these aremore expensive and less convenient .in use.

Furfurol (O,H,,O,) is a volatile oil obtained when wheat-bran, sawdust, madder-root, or

other substance is acted on by dilute sulphuric acid with repeated distillations. It is nearly colorless when first prepared, but turns yellow in the dark, and brown when exposed to light. Fueusol is made in the same way, only substituting sea-Weeds.

Having stated the nature of my invention and described the manner of performing the same, I declare that what I claim, and desire to seen re byLettcrs Patent of theUnited States,

The process of manufacturing carbons for electric lamps, which consists in treating (either alone or combined with lamp-black) 

